Process for polymerising olefin with a Ziegler-Natta catalyst

Abstract

The present invention relates to a process for (co-)polymerizing olefin(s) comprising introducing into a polymerization medium the olefin(s), a titanium-based catalyst of Ziegler-Natta type, an organometallic cocatalyst and a halogenated hydrocarbon compound in an amount effective for increasing the catalyst activity in the (co-)polymerization, the amount being such that the molar ratio of the quantity of the halogenated hydrocarbon compound to that of titanium is comprised between 0.01 and 0.1, or between 0.001 and 0.15 when the (co-)polymerization is carried out continuously. The process is particularly useful in a continuous gas-phase (co-)polymerisation of olefin(s).

I claim: 
     
       1. Process for increasing the catalyst activity of a gas-phase (co-)polymerisation of ethylene or ethylene with at least one C 3  -C 8  olefin, comprising introducing into the gas-phase (co-)polymerisation medium the olefin(s), a titanium based catalyst of the Ziegler-Natta type essentially containing atoms of titanium, halogen and magnesium, and optionally a refractory oxide, and an alkylaluminium cocatalyst, wherein the (co-)polymerisation is conducted continuously in the gas phase and a mono- or polyhalogenated saturated hydrocarbon compound is continuously introduced into the gas-phase (co-)polymerisation medium in an amount such that the molar quantity of the mono- or polyhalogenated saturated hydrocarbon compound to that of titanium introduced into the gas-phase polymerisation medium is from 0.03 to 0.095. 
     
     
       2. Process according to claim 1, characterized in that the halogenated hydrocarbon compound is introduced in a quantity such that the molar ratio of the quantity of the halogenated hydrocarbon compound to that of titanium introduced into the polymerization medium is in the range from 0.031 to 0.091. 
     
     
       3. Process according to claim 1, characterized in that the alkylaluminum cocatalyst is introduced in a quantity such that the molar ratio of the quantity of the halogenated hydrocarbon compound to that of the alkylaluminum cocatalyst introduced into the polymerization medium is comprised between 0.001 and 0.5. 
     
     
       4. Process according to claim 1, characterized in that the halogenated hydrocarbon is selected amongst the group consisting of methylene chloride, chloroform, carbon tetrachloride, trichloro-1,1,1 ethane and dichloro-1,2 ethane. 
     
     
       5. Process according to claim 1, characterized in that the catalyst is prepared by a method comprising: (1) a reaction between a magnesium metal, a halogenated hydrocarbon and at least one tetravalent titanium compound,   (2) or bringing a granular support into contact with (a) a dialkylmagnesium and optionally a trialkylaluminium, (b) a halogenated hydrocarbon and (c) a tetravalent titanium compound,   (3) or bringing a magnesium chloride support into contact with (a) an alkylaluminum compound suitable for reducing a titanium compound and (b) a tetravalent titanium compound.   
     
     
       6. A process as defined in claim 1 wherein said polyhalogenated hydrocarbon is chloroform.